A wireless local area mesh network, also called a wireless LAN-based ad hoc network, consists of two or more nodes interconnected via radio links and communicating with each other directly or indirectly. It may connect to the Internet or other networks through a portal. In wireless local area mesh networks, the IP layer routing protocols have been used to discover the route from a source node to a destination node. The IP layer ad hoc routing protocols are based on the IP addresses. However, some devices, such as WLAN access points, forward data packets based on the IEEE 802.11 media access control (MAC) address and only operate at the link layer (Layer 2). In addition, data forwarding at Layer 2 is generally faster than that at the IP layer (Layer 3) because the data packets do not have to pass to the IP layer.
The Ad Hoc On-Demand Distance Vector (AODV) protocol is an ad hoc routing protocol that operates at the IP layer. It can support unicast and multicast route discovery. Routes are discovered on an on-demand basis. When a source wants to send a packet to a destination node, it discovers the route to the destination by broadcasting a route request message over the network if it does not have and needs a valid route to the destination node. The message contains the IP addresses of the source node and destination node along with other necessary information. The destination node or the node with a valid route to the destination node replies to this request by sending a route reply to the source node. The route request and route reply messages establish the routing table in each of intermediate nodes for forward and reverse paths/routes. The established routes expire if they are not used within a given route lifetime. The on-demand routing reduces the effects of stale routes due to network topology changes (for example, to node mobility and failures) and the need for maintaining unused routes. However, it introduces route discovery delay because the source node needs to establish the route before it is able to send the data. The source node also needs to buffer the data during the route discovery period.
The Destination-Sequenced Distance Vector (DSDV) is a proactive routing protocol for wireless local area mesh networks. The nodes in the network exchange routing control messages so that the routing table at each node contains the routing information to all the destination nodes in the wireless local area mesh network. The data packets are forwarded from the source node to the destination node by the intermediate nodes based on the routing tables along the path. To maintain the valid routes and to avoid the routing loops due to the link/node failure and network topology changes, each node not only periodically transmits route updates but also broadcasts the updates immediately when significant new information is available. Although the DSDV permits packets to be forwarded using either layer-2 MAC addresses or layer-3 IP addresses and there is no route discovery delay, it incurs a relative high routing overhead because of network-wide routing message broadcasts. Especially when the nodes in a network move quite fast and the network topology changes frequently, a large portion of network capacity is used to keep the routing information current. In addition, some nodes may not forward the data packets originated from other nodes due to processing and battery limitation or other reasons. However, the above protocols assume that each node agrees to relay data packets to other nodes upon request and does not consider the non-forwarding nodes.
In a wireless local area mesh network, two or more nodes are interconnected via IEEE 802.11 links. Each node has a unique IEEE 802.11 Media Access Control (MAC) address. When a source node sends data packets to a destination node, it needs to know the path/route from the source node to the destination node.
What is needed is a routing mechanism to discover and establish the path based on the destination MAC address. The problem solved by the present invention is how a source node discovers and establishes the path to the destination node based on the destination's IEEE 802.11 MAC address in a wireless local area mesh network.